DISCUSSION
Previous studies have shown an impairment in the quality of life in patients with congestive heart failure.13 14 Our aim in the present study was to make a more detailed analysis of the relation between quality of life, the severity of the disease, and objective functional variables. Quality of life was assessed with a well validated questionnaire, the SF-36.15 16 For determining maximal and submaximal functional capacity, standard methods were employed. In order to ensure accuracy, all data were collected within a 48 hour period in each patient.
Comparison with the general population
Compared with the healthy general population, the congestive heart failure sample showed a global reduction in quality of life in all the SF-36 scales. All indices of quality of life decreased with NYHA functional class, the most pronounced loss of quality of life being observed in the domains of physical functioning, role function physical, and role function emotional. In apparently asymptomatic patients with left ventricular dysfunction, independently classified as NYHA functional class I, the SF-36 revealed mild but significant decreases in the scales representing somatic aspects and vitality. In NYHA classes II and III all aspects of quality of life were dramatically reduced, reflecting the severe impact of congestive heart failure on daily life, even though the patients were in a compensated stage and in an ambulatory setting. Comparison of the present study sample with a sample of patients with congestive heart failure of the medical outcome study26 revealed a similar pattern of impairment. However, as the latter did not include objective functional variables such as the six minute walk test and peak oxygen uptake, a comparison between the two samples can only be limited.
Comparison with other chronic diseases
A previous sample of patients on chronic haemodialysis25 showed nearly the same profile as the overall congestive heart failure sample in our present study. Thus it could be argued that all chronic disease conditions have a similar impact on quality of life. However, patients with chronic hepatitis C24 were characterised by quite a different pattern. In scales referring more to physical health, patients with chronic hepatitis C resembled patients with congestive heart failure in NYHA class I. However, in scales referring to mental health, hepatitis C patients were more comparable to NYHA class II patients. As expected, patients with major depression were in a better physical condition than patients with congestive heart failure. Most interestingly, the patients with congestive heart failure in NYHA class III had a similar impairment of quality of life in the mental health domains as patients with major depression, in addition to their already dramatically reduced
physical health. These data are in accord with the findings of some recent studies showing that a large proportion of patients with congestive heart failure suffer from depression.28–30 Thus the quality of life in patients in NYHA class III is reduced not only physically but also mentally. One could speculate that these results reflect the effects of congestive heart failure on the central nervous system. Changes in central neurohumoral regulation systems or diminished central perfusion might impair cognitive capacity and trigger a latent vulnerability to depressive disorders.31
Relation of NYHA class, peak oxygen uptake, six minute walk test, left ventricular ejection fraction, and quality of life
In addition to NYHA functional class, more objective indices of functional capacity—such as peak oxygen uptake and the six minute walk test—also showed some relation to the quality of life. This contrasts with the report by Steptoe and colleagues,18 who found no univariate association between exercise capacity and quality of life in patients with mild to moderate congestive heart failure (predominantly in NYHA classes I and II); however, our present study included a broader spectrum of patients with congestive heart failure, with a large proportion in NYHA class III. Cardiopulmonary exercise testing and the six minute walk test represent different aspects of functional capacity, as only the latter—a submaximal exercise test—reflects the work load of daily activities.21 However, in accordance with the close relation between both these exercise tests,20 all SF-36 scales were related similarly to peak oxygen uptake and to the six minute walk test. In contrast, the left ventricular ejection fraction was not significantly correlated with any of the short form scales. Furthermore, there was no difference in health related quality of life in patients subgrouped according to their ejection fraction. This finding confirms the lack of relation between left ventricular ejection fraction and disease specific quality of life observed in other studies.32 33 The findings of our present study may also explain why β blocker treatment in congestive heart failu